Do twins happen more often in the animals or in humans?

Answers

That depends on the animal. Some animals like cats and dogs are made to have multiples. I was able to find statistics on the average number of twins born to humans and cows, and it seems that, depending on the cow species they win for more natural twin births. With humans, in 2006 (numbers released in 2009) the average twin birth rate was 32.2 of every 1000 births, essentially the same as the previous two years. However, in Holstein dairy cows, the rate was 8.9%, meaning about 89 out of every 1000 births. Conversely, Hereford cattle had only 4 twins out of every 1000 births.